A nozzle plate of an ink-jet head includes nozzle holes for discharging ink. In the ink-jet head, in many cases, the surface of the nozzle plate is kept ink-repellent in order to prevent excess ink from remaining in the vicinity of the nozzle holes when ink is discharged from the nozzle holes.
As regards this ink-jet head, there is known a technique of performing, with a suction nozzle, suction-cleaning of ink or the like which adheres to the nozzle plate in the vicinity of the nozzle holes. For example, there have been proposed such methods as performing suction-cleaning by sliding a suction nozzle while keeping the suction nozzle in contact with the neighborhood of nozzle holes on the nozzle plate, or performing suction-cleaning by moving a suction nozzle while keeping a gap between the suction nozzle and the nozzle plate so that the suction nozzle may not come in contact with the nozzle plate. Besides, if the suction force of the suction nozzle acts in a vertical direction of an ink discharge direction from nozzle holes, the ink may easily be pulled off in the vicinity of the nozzle holes, leading to a factor of occurrence of bubbles in the nozzle. In order to avoid this, there has been proposed a structure of the suction nozzle, which takes into account such a flow of air that the suction force acts in a direction crossing the ink discharge direction.
The surface of the nozzle plate repels ink, since the surface of the nozzle is treated so as to have ink repellency in order to stabilize the ink discharge capability. Thus, when suction-cleaning has been performed by the suction nozzle, ink tends to remain on the surface of the nozzle plate in the form of minute ink drops, and such residual ink drops are hardly moved by the air flow alone. Consequently, the residual ink cannot be removed from the surface of the nozzle plate, and minute ink drops remain. As a result, the ink repellency in the vicinity of nozzle holes of the surface of the nozzle plate may deteriorate, and the quality of printing may be degraded.